An Efficient Search Strategy for Block Motion Estimation Using

Image FeaturesDigital Video Processing 1 Term Project

Feng LiMichael Su

Xiaofeng Fan

Fast Search in Block Motion Estimation

Block motion estimation using the full search is very computational demanding. 225 search points in a 15x15 search window with

displacement vectors from -7 to 7 in X, Y directions.

Fast search algorithms to reduce the amount of computations by limiting the number of locations to be searched.

Fast search algorithms can be trapped on the local minimum in the search process.

Nonuni-modal error surface tested by a checking block

MAD error surface for two different blocks

Fast search improvement

Place the checking point as close as possible to the global minimum.

Multiple starting search points.Eliminate the unnecessary starting points

using image features. Points, Lines and Edges can be used as

the image features.

Regular Starting point pattern: Starting points distribute evenly across the search window

Image Features Edge-Assisted Search (EAS)

Edges are used as the image features.The number of search points are dynamic

on each block.Less search points are used for smooth

region.More search points are needed in blocks

containing many edges and motions.

Image Features Edge-Assisted Search (EAS)

Image preprocessing Smoothing of the frame. Edge Detection using 3x3 Sobel gradient

convolution masks.

1 2 1 1 0 1

0 0 0 2 0 2

1 2 1 1 0 1x yg g

' '( , ) ( , )t t x t yS I i j g I i j g

Adjustment of the Regular Starting Point Pattern

Convert into the binary image by threshold. Edge matching score (EMS) to eliminate the

unnecessary starting points.

1 ( ( , ))( , )

0t e

t

if S i j TB i j

otherwise

1 1 1 1

10 0 0 0

( , ) ( , ) ( , )N N N N

t ti j i j

EMS u v B i j B i u j v

min_ _ _k k in updated SPPG MAD MAD

Flowchart of the EAS

Example 1

Image Block (15X15) and edge difference distribution

Image Block (25X25) and edge difference distribution

Block Intensity difference

Test result 1: Displacement Vectors for Example 1

Example 2

Test result 2: Displacement Vectors for Example 2

Performance Evaluation

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Full

3step

Diomand

EAS+3step

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EAS+3step

Thank you

Questions?